package org.apache.lucene.analysis.fr;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.analysis.Token;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;

import java.io.IOException;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/**
 * A filter that stemms french words. It supports a table of words that should
 * not be stemmed at all. The used stemmer can be changed at runtime after the
 * filter object is created (as long as it is a FrenchStemmer).
 *
 */
public final class FrenchStemFilter extends TokenFilter {

	/**
	 * The actual token in the input stream.
	 */
	private FrenchStemmer stemmer = null;
	private Set exclusions = null;

	public FrenchStemFilter( TokenStream in ) {
          super(in);
		stemmer = new FrenchStemmer();
	}


	public FrenchStemFilter( TokenStream in, Set exclusiontable ) {
		this( in );
		exclusions = exclusiontable;
	}

	/**
	 * @return  Returns the next token in the stream, or null at EOS
	 */
	public final Token next(final Token reusableToken)
		throws IOException {
                assert reusableToken != null;
                Token nextToken = input.next(reusableToken);
		if (nextToken == null)
			return null;

		String term = nextToken.term();

		// Check the exclusion table
		if ( exclusions == null || !exclusions.contains( term ) ) {
			String s = stemmer.stem( term );
			// If not stemmed, don't waste the time  adjusting the token.
			if ((s != null) && !s.equals( term ) )
			   nextToken.setTermBuffer(s);
		}
                return nextToken;
	}
	/**
	 * Set a alternative/custom FrenchStemmer for this filter.
	 */
	public void setStemmer( FrenchStemmer stemmer ) {
		if ( stemmer != null ) {
			this.stemmer = stemmer;
		}
	}
	/**
	 * Set an alternative exclusion list for this filter.
	 */
	public void setExclusionTable( Map exclusiontable ) {
		exclusions = new HashSet(exclusiontable.keySet());
	}
}


